A man repays a loan of $3250 by paying $20 in the first month and then increases the payment by $15 every month. How long will it take him to clear the loan?
At the end of the n-th month the total payment is:
Using Gauss' formula for the sum of the first
express this as an equation in
Obviously we discard the negative solution and
So the debt is repaid at the end of the 20-th month.